1. Technical Field
This invention relates to a process for the electrolytic production of aluminum. In one aspect, this invention relates to a novel process for the electrolytic production of aluminum using a fuel cell.
2. Background
Aluminum metal is produced commercially by the electrolytic smelting of alumina. Bauxite alumina ore is refined in a Bayer plant, and the refined alumina is smelted in an electrolytic bath of molten salts in a Hall-Heroult cell plant. These molten salts include cryolite (3NaF--AlF.sub.3) and minor additions of salts such as LiF and CaF.sub.2. Actual Hall-Heroult cell bath contains less NaF than the specific composition formula of 3NaF-AlF.sub.3 and varies somewhat from plant to plant. Relatively pure refined alumina is reduced in the molten salts in the Hall-Heroult electrolytic cell, named Hall-Heroult after the earliest independent inventors of the electrolytic process for producing aluminum.
The electrolytic smelting reaction is carried out in the Hall-Heroult cell process in an aluminum reduction pot in which alumina is dissolved in the molten salt bath. The alumina in solution in the molten salt is electrolyzed to form metallic aluminum. Aluminum metal produced in the reaction is heavier than the electrolyte and forms a molten layer at the bottom of the reduction pot which serves as the cathode of the cell. Carbon anodes extend into the bath, and oxide ions react electrochemically with the carbon to produce carbon dioxide, which is liberated at the anode.
The cost of making aluminum has not changed very much in the past few decades. Those changes that have taken place have been incremental, evolutionary changes in the fundamental Hall-Heroult process.